C-MAP 4D NA-D941 Block Island to Norfolk [M-NA-D941-MS]C MAP 4D NA D941 Block Island to Norfolk The next evolution in navigation solutions. C MAP 4D adapts to your boating needs because it's the only digital chart that offers advanced features and lets you add data and services as they become available. Full 4D Content When you choose Full 4D content you will experience the latest in navigation data and technology such as: 3D Chart View The world has three dimensions. When you add the 4th dimension of